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Abstract
The composition and biosynthesis of glycoproteins, proteoglycans, and gangliosides have been studied in a clonal line of rat pheochromocytoma (PC12) cells. Glycoproteins account for approximately 78% of the glucosamine-labeled complex carbohydrates found in the culture medium, together with 17% chondroitin sulfate and 5% heparan sulfate. 10% of the glycoproteins but less than 1% of the proteoglycans are released by trypsin treatment of the cells, whose complex carbohydrates are composed of 93% glycoproteins, 1.3% chondroitin sulfate, 3.4% heparan sulfate, and 2.6% of mono- and disialogangliosides. Sequential lectin affinity chromatography and alkali treatment of glycopeptides prepared from the medium, trypsin-releasable, membrane, and cell-soluble glycoproteins demonstrated that in all of the subfractions large tri- and tetraantennary complex oligosaccharides account for 82 to 97% of those present in PC12 cell glycoproteins. Biantennary oligosaccharides account for approximately 2-6% of those in medium and trypsinate, as compared to 10-13% in the membrane and cell soluble glycoproteins, and there were large differences (ranging from 7 to 60%) in the proportions of biantennary oligosaccharides which are substituted by fucose on the core N-acetylglucosamine which is linked to asparagine. High mannose oligosaccharides are present predominantly in the cell membrane and soluble glycoproteins, where they account for 4 to 5% of the total glycoprotein labeling. In response to nerve growth factor (NGF), the PC12 cells extend long processes and acquire other properties similar to those of differentiated sympathetic neurons. Significant alterations were also observed in the complex carbohydrates of NGF-treated cells, the most striking of which were an almost 3-fold increase in labeled gangliosides and a 75% increase in trypsin-releasable glycoproteins. Cellular heparan sulfate decreased by 70% in response to NGF and increased by an equivalent amount in the culture medium, whereas an NGF-induced increase in chondroitin sulfate labeling occurred specifically in the cell membranes.
Highlights
From the Departmentof Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York 11203 and the Department of Pharmacology, New York University School of Medicine, New York, New York 10016
Gly- mal adrenalchromaffii cells.in the presence of coproteins account for approximately 78% of the glu- nanogram levels of NGF,’ PC12 cells cease to divide, extend cosamine-labeled complexcarbohydrates found in the long microtubule-containing processes, and acquire electrical culture medium, together with 17%chondroitin sulfate and 5% heparan sulfate. 10% of the glycoproteins but less than1%of the proteoglycans are released by trypsin treatment of the cells,whosecomplex carbohydrates are composed of 93% glycoproteins, 1.3% chondroitin sulfate, 3.4%heparan sulfate, and 2.6% ofmonoand disialogangliosides
Sequential lectin affinity chromatography and alkali treatment of glycopeptides prepared from the medium, trypsin-releasable, membrane, excitability and increased sensitivity to acetylcholine (Greene and Tischler, 1976; Dichter et al, 1977).These findings indicate that theeffect of nerve growth factor on PC12 cellsis to convert them into sympathetic neuron-like cells
Summary
(,NGF produces a40% increase inthe labeling of medium glycoproteins andproteoglycans when expressed in relatitooncell protein.)In all cases, glycoproteins are the major labeled components, accounting for 78 and 92%of the total mediumand cell radioactivity, respectively. 1.16 0.76 case of heparan sulfate almost three-quarters is present in the membranes and the remainder is in the soluble fraction. Cells their TLC migration distances with those from brain (Fig. 1)
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